1. Field of the Invention
This invention relates to magnetic tape drives; and more particularly, to a tape cartridge drive with a movable read/write head.
2. Description of the Prior Art
In recent years, computer technology has greatly expanded the market for computers, including reasonably inexpensive small computers, such as personal computers and computers for small businesses. The so-called floppy disk drives provide a common means of data storage for small computers. One floppy disk drive in common use today is the industry standard 51/4 inch minifloppy disk drive. One or more of these disk drives are typically mounted inside the computer console. A diskette is inserted or removed through one or more slots in the front of the console. In other applications, the minifloppy disk drive is contained in a separate housing for use externally to the computer console. In either instance, it has become an industry practice to provide a 51/4 inch minifloppy disk drive as a package with standard exterior dimensions.
Floppy disk drives have proved to be convenient for many applications, such as program loading and data interchange, but they have a limited data storage capacity. Because of this problem, larger capacity disk drives, such as the so-called Winchester disk drives, have been used in lieu of floppy disk drives in applications requiring greater data storage capacities. The Winchester-type disk drive generally comprises one, two, or three hard disks on which data are recorded. A Winchester-type disk drive can provide a much higher data storage capacity and faster data access and data transfer times than a floppy disk drive. Accordingly, a common practice in small business applications is to use a combination of the minifloppy disk and the Winchester disk. In this way, the day's transactions can be recorded on one or two floppy disks, and a full copy of the business's transactions can be made on a hard disk at weekly intervals or longer.
Recently, Winchester-type disk drives have been manufactured in a package with the same exterior dimensions and mounting hole locations as a standard 51/4 inch minifloppy disk drive. In this way, the Winchester disk drive can be conveniently installed in the computer console in place of a minifloppy disk drive to provide the larger data storage capacity.
Data storage for computer applications also can be provided by magnetic tape drives instead of disk drives. In recent years, 1/4-inch cartridge tape drives have been replacing floppy disk drives in many applications because the tape cartridges are more compact, they can store from about 15 to 50 times more data than diskettes, and they have a lower cost per megabyte.
Tape cartridges, such as the Scotch DC 300XL data cartridge made by 3M Co., are commonly used for data storage in cartridge drives. Briefly, this type of standard tape cartridge includes a 1/4-inch magnetic tape enclosed within a case. The tape is driven, in part, by an internal capstan, a portion of which is exposed at an edge of the cartridge case. When the cartridge is inserted into a receptacle in the tape drive unit, the exposed capstan engages a capstan driven by the tape drive motor for driving the tape. The tape cartridge also includes a door near a corner of the case. The cartridge door is normally springbiased to a closed position for protecting the tape during storage and transport. When the cartridge is inserted in the tape drive unit, the door is tripped open to expose a portion of the tape for engaging the magnetic read/write head on the tape drive unit. The head projects into the cartridge envelope to contact the tape under the proper operating tension. The mechanism for guiding the cartridge into the receptacle not only trips the door open, but it also prevents the door from contacting the read/write head when the cartridge is inserted or removed.
The magnetic tape cartridges used in magnetic tape drives are manufactured according to industry standards approved by the American National Standards Institute (ANSI), Magnetic tape drives, including the larger 1/2-inch tape drives, have been able to replace the industry standard larger disk drives, such as the 8-inch, 101/2 inch and 14-inch disk drives. However, the standard 1/4-inch tape drive units have not been able to replace either the 51/4 inch minifloppy disk drive or the Winchester-type disk drive, because the ANSI standard size 1/4-inch tape cartridge has been too large to fit into a tape drive unit that meets the industry standard exterior dimensions of the 51/4 inch disk drives. For instance, the standard exterior width of a 51/4 inch disk drive package is 5.75 inches. With the ANSI standard size tape cartridge inserted in a standard tape drive, and with the cartridge door held open to expose the tape, the cartridge case and the cartridge door in its open position cover a distance of 5.765 inches, i.e., a distance greater than the standard 5.75 -inch width of the smaller disk drives.
The present invention provides a magnetic tape drive that allows an ANSI standard tape cartridge to be inserted into a tape drive package having the same industry standard exterior dimensions as the 51/4 inch disk drives.
The ANSI standard exterior dimensions of a 1/4-inch tape cartridge are 4 inches by 6 inches (when the cartridge door is closed). U.S. Pat. No. 4,498,112, issued Feb. 5, 1985, entitled "Tape Cartridge Receptacle", discloses a tape drive unit which allows a 1/4-inch tape cartridge to be inserted into a tape drive housing having the same exterior dimensions as the 51/4 inch disk drives. In that tape drive unit, the cartridge is front-loaded into the receptacle, i.e., the cartridge is inserted with its long dimension facing the mounting slot on the front wall of the tape drive housing. The amount of space taken up by this tape drive unit adjacent a computer console can be reduced if the tape drive housing is turned 90.degree. so its short dimension (the end face of the unit) faces forward adjacent the computer console. This would require loading the cartridge into the tape drive unit endwise, i.e., inserting the cartridge lengthwise with its short dimension facing a shorter mounting slot in the end wall of the housing. However, if the tape cartridge is loaded endwise, the read/write head would normally interfere with sliding the cartridge case into the tape drive unit. The head would be in the way in this instance because it normally protrudes into the tape cartridge envelope.
The present invention provides a tape drive unit with a movable read/write head which allows a tape cartridge to be inserted endwise into the housing and removed from the housing without interference with the read/write head. Once the tape cartridge is in place in the unit, the read/write head is moved into an operating position for applying the proper operating tension to the tape. The head is retracted prior to removing the cartridge from the tape drive housing.
When inserting the tape cartridge endwise into the tape drive housing, there is a need to ensure that the read/write head is not moved into the operating position until the tape cartridge is fully inserted into the unit and the cartridge door is held open. There is also a need to ensure that the cartridge cannot be removed from the housing while the head is in its operating position. The head must be fully retracted before the cartridge can be removed.
The present invention provides a fail-safe mechanism that cooperates with the movable read/write head to permit the cartridge to be fully inserted into the tape drive unit with the cartridge door held open before the head is moved to its operating position. The fail-safe mechanism also prevents removal of the cartridge if the head is in its operating position, and the cartridge cannot be removed from the tape drive unit until the head is fully retracted.